CODEWITHSUNDEEP
javascriptnode.jsasync-awaitpuppeteerheadless
D. Sikilai
D. Sikilai

Reputation: 497

node.js puppeteer evaluate() returning Unexpected objects. throws TypeError each time

I Cannot understand why the following code complains check() is not a function. when i make it an object with the target function it again complains that no such function is found. I have tried to resolve this problem for like 6 hours now. any help will be appreciated...

 const browser = await puppeteer.launch({headless: false});
    const page = await browser.newPage();
    await page.goto('https://bet254.com');

 const check=await page.evaluate(() => {
            return function () {
            try {
                return document.getElementsByClassName("header-buttons")[0].childNodes[0].textContent.trim() !== "Login";
            } catch (e) {
                console.log(e);
                return false;
            }
        }
 });
if (check()) {
        console.log("Logged in already!");
    } else {}

The following is the error:-

(node:9632) UnhandledPromiseRejectionWarning: TypeError: check is not a function
    at D:\void\js_\node_puppeteer\entry.js:19:9
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:9632) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:9632) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Upvotes: 1

Views: 2389

Answers (2)

vsemozhebuty
vsemozhebuty

Reputation: 13782

Unfortunately, page.evaluate() can only transfer serializable values (roughly, the values JSON can handle). Functions are not serializable. So you can try, for example, one of these ways:

const browser = await puppeteer.launch({headless: false});
const page = await browser.newPage();
await page.goto('https://bet254.com');

const check = await page.evaluate(() => {
    return document.getElementsByClassName("header-buttons")[0].childNodes[0].textContent.trim() !== "Login";
});

if (check) {
    console.log("Logged in already!");
} else {}

const browser = await puppeteer.launch({headless: false});
const page = await browser.newPage();
await page.goto('https://bet254.com');

function check(page) {
  return page.evaluate(() => {
      return document.getElementsByClassName("header-buttons")[0].childNodes[0].textContent.trim() !== "Login";
  });
}

if (await check(page)) {
    console.log("Logged in already!");
} else {}

Upvotes: 3

linxf
linxf

Reputation: 11

You should look for answers from official documents instead of asking questions here. Here is the document about the method of this function. you should understand from the last line

page.evaluate(pageFunction[, ...args])
pageFunction <[function]|[string]> Function to be evaluated in the page context
...args <...[Serializable]|[JSHandle]> Arguments to pass to pageFunction
returns: <[Promise]<[Serializable]>> Promise which resolves to the return value of pageFunction
If the function passed to the page.evaluate returns a [Promise], then page.evaluate would wait for the promise to resolve and return its value.
If the function passed to the page.evaluate returns a non-[Serializable] value, then page.evaluate resolves to undefined. DevTools Protocol also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity, and bigint literals.

Upvotes: 0

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